1. Field of the Invention
The invention relates to a method of producing microstructured metallic bodies on an electrically conductive base plate by one of electron beam lithography, X-ray lithography and micromolding wherein cavities of negative molds are filled with metal.
2. Description of the Related Art
Methods of this type are disclosed in German Patent Nos. 3,712,268 and 3,206,820. According to German Patent No. 3,712,268, a resist layer sensitive to X-ray radiation is applied onto a metallic carrier layer, e.g. of chromium nickel steel, and is partially exposed to synchrotron radiation through an X-ray mask. The exposed regions are dissolved out with a liquid developer, thus creating cavities corresponding to the microstructures which are filled by electroplating with a metal, employing the metallic carrier layer as an electrode. Thereafter, the remaining resist layer and, depending on the intended use for the microstructured body, also the carrier layer can be removed. With these X-ray deep-etch lithography electroforming processes, also abbreviated as the LIGA process, microstructures can be generated which have a very high aspect ratio and smallest lateral dimensions in the micron range. The same applies for electron beam lithography. In connection with the production of negative molds from these electron beam or X-ray sensitive plastics in the form of columns or pins having a very small base surface, the problem arises that individual columns or pins do not adhere sufficiently to the carrier plate and therefore may be rinsed away by developer fluid.
In a micromolding technique disclosed in German Patent No. 3,206,820, end faces of microstructures of a molding tool and a corresponding surface of a carrier plate must be extremely planar and must be pressed against one another under high pressure to prevent plastic introduced in liquid form from seeping in between these surfaces and interfering with the electroshaping, which likewise leads to losses of structure.
German Published Patent Application 3,335,171.A1 discloses a method of producing microstructures in which, after completion of production of a plastic mold from a positive or original shape, initially a photolacquer film which had previously been applied to a surface of an electrically conductive base plate of a molding tool and which is to undergo an intimate bond with a molded plastic substance during a molding process, remains at the bottom of a plastic negative mold and is removed before electroforming of the positive product. For the removal of the photolacquer film at the bottom of the plastic negative mold, irradiation with UV light and subsequent dissolving away by means of a developer solution are proposed. However, such photolacquer films have no optimum adhesion promoting characteristics, which is why this method has not found acceptance in practice.